Both transparent and opaque plastic films are used as wrapping and/or packaging materials in substantially every area of manufacturing and marketing of modern commerce. The plastic packaging materials include rigid materials which provide protection from outside impact or crushing forces, including the somewhat flexible but brittle packaging materials which provide a form fit around the product. This type of plastic packaging material may typically be heated so that it shrinks around the product. In addition, pliable plastic films which vary from being extremely thin and flexible to those which are substantially thicker and less pliable are used which do not always protect the product from outside crushing or impact forces, but do provide excellent protection from an undesirable environment, such as moisture, dirt, sand, corrosive air or gases, etc. The present invention is primarily concerned with pliable materials such as plastic used in packaging which must effectively seal the packages contents from the environment and/or contamination.
More particularly, the present invention is concerned with removing all folds and wrinkles in two confronting edge portions of the packaging material at the open end of a package prior to sealing or bonding the two confronting edges one to the other to create a liquid and/or air tight package. Removing the folds or wrinkles in the two confronting edge portions helps to insure that the resulting seal will be fluid tight. Tests on a prototype apparatus incorporating the features of this invention indicate that the rejection rate caused by ineffective seals can be decreased from from around 15% to 20% down to substantially zero.
Therefore, it is an object of this invention to provide methods and apparatus for removing folds and wrinkles in confronting portions of an edge prior to sealing or bonding the open edge.
It is another object of this invention to provide simple and inexpensive apparatus and methods for preparing the edge portion of an open pliable plastic package prior to sealing the edge of the package so as to facilitate achieving a liquid and/or air tight package.
Although the applicant is not aware of any prior art references or actual apparatus which is similar to the apparatus and methods of the present invention, some prior art references which illustrate the known state of the art include U.S. Pat. No. 4,723,390 issued to the present inventor Horace W. Duke on Feb. 9, 1988; U.S. Pat. No. 3,621,632 issued to S. A. C. Browining on Nov. 23, 1971; U.S. Pat. No. 3,552,088 issued to Akiro Niwa on Jan. 5, 1971; U.S. Pat. No. 3,471,990 issued to J. A. Bonuchi et al on Oct. 14, 1969; U.S. Pat. No. 3,420,034 issued to A. B. Saraisky et al on Jan. 7, 1969; and U.S. Pat. No. 3,163,969 issued to J. F. Irwin et al on Jan. 5, 1965.
The Browing and Irwin et al patents deal with closing the end of a plastic bag around a loaf of bread, and both patent specifications show how the open end of the bag of bread is gathered and then the gathered plastic material is enclosed and held closed with a closure tie or device.
The Niwa patent discloses apparatus for individually and successively packaging articles by the use of continuous sheets of heat-sealable packaging material. The apparatus also shows the sealed package being separated or cut from the continuous packaging material.
The Bounchi et al patent discloses packaging apparatus which has heating structure for producing a line of seal across the initially open end of a polyethylene bag containing poultry products. The apparatus includes a sponge which clamps against the package prior to sealing to expel air so as to produce a tight package. The apparatus also provides a pair of opposed rollers which receive the initially open end of the bag and pulls the end away from the remainder of the bag to stretch the bag over the product so as to allow removal of excess material.
The Saraisky et al patent discloses apparatus for packaging articles in a close-fitting package without the necessity of shrinking the wrapper or expanding the article after sealing the package. The close fitting package is accomplished by incorporating with the heat-sealing means a heat-shielding sheet material-fitting means arranged to draw the wrapping material towards and tightly against substantially all of the exterior surfaces of the article being wrapped. This includes drawing the material tight against the surfaces immediate adjacent to the seal, while shielding the sheet material and the article from the heat arising from the heat-shielding means except at the point that the seal is being formed so as to eliminate loose wrapping material around the package.
Thus, although all of the above discussed patents deal with closing a pliable plastic packaging material around a product, and although the Duke, Niwa, Bonuchi, and Saraisky patents deal with sealing confronting edge material of a package, none of the patents teach or even suggest the unique apparatus and methods of the present invention for substantially eliminating all wrinkles and folds from such confronting edges of a package prior to sealing.